Slideshow: The 10 Best National Parks

The National Park Service protects some of the most spectacular scenery in the United States -- and each year, the parks see more than 280 million visitors. In a recent survey, readers at review site TripAdvisor chose their top 10 favorite national parks across the U.S. Encompassing mountains, sand dunes, waterfalls, craggy cliffs, canyons and volcanoes, these parks showcase the breathtaking range of America's geography.